#!/bin/bash

usage() {
  echo "Usage: $0 -u <url> [-w <warning>] [-c <critical>] [-C <contains>] [-L] [-I] [-H <headers>] [-p] [-R] [-s]"
  echo "[Arguments]:
  -u Specify the URL to check (required).
  -w Set the warn level for response time (default: 1 second).
  -c Set the critical level for response time (default: 2 seconds).
  -C If the body does not contain this string, return CRITICAL.
  -L Follow redirects.
  -I Insecure mode (--insecure).
  -H Specify headers. Formatted like \"Header1: value,Header2: value\"
  -p Print the curl command and exit
  -R Set curl --resolve option.
  -M Set the HTTP mode (default: GET)
  -t Timeout in seconds
  -s Ignore the response status code.
  -e Specify the exact response code that should be returned. Cannot be used with -s option.
  -e Expected status code.
  -S Sanitize HTML when printing to console. Good for Icinga2 Web.
  -n Don't return any perfdata if the status code was not 200."
  exit 3
}

# Default values
WARN_TIME=700
CRIT_TIME=1000
FOLLOW_REDIRECTS=""
INSECURE=""
HEADERS=""
PRINT_CURL=""
RESOLVE=""
IGNORE_STATUS=""
TIMEOUT="30"
HTTP_METHOD="-X GET"
EXPECTED_STATUS_CODE=""
SANITIZE_HTML=false
DISABLE_PERFDATA=false

# Parse arguments
while getopts "u:w:c:C:LH:M:IpR:st:e:hSn" opt; do
  case $opt in
  u)
    URL="$OPTARG"
    ;;
  w)
    WARN_TIME="$OPTARG"
    ;;
  c)
    CRIT_TIME="$OPTARG"
    ;;
  C)
    CRIT_STRING="$OPTARG"
    ;;
  L)
    FOLLOW_REDIRECTS="-L"
    ;;
  I)
    INSECURE="--insecure"
    ;;
  H)
    HEADERS="--header $OPTARG"
    ;;
  p)
    PRINT_CURL="yes"
    ;;
  R)
    RESOLVE="--resolve $OPTARG"
    ;;
  s)
    if [ -n "$EXPECTED_STATUS_CODE" ]; then
      echo "Cannot use -s option with -e option"
      exit 3
    fi
    IGNORE_STATUS="yes"
    ;;
  t)
    TIMEOUT="--max-time $OPTARG"
    ;;
  M)
    HTTP_METHOD="-X $OPTARG"
    ;;
  e)
    EXPECTED_STATUS_CODE="$OPTARG"
    ;;
  h)
    usage
    ;;
  S)
    SANITIZE_HTML=true
    ;;
  n)
    DISABLE_PERFDATA=true
    ;;
  e)
    if [ "$IGNORE_STATUS" = "yes" ]; then
      echo "Cannot use -e option with -s option"
      exit 3
    fi
    EXPECTED_STATUS_CODE="$OPTARG"
    ;;
  *)
    echo "Invalid option: -$OPTARG" >&2
    usage
    exit 3
    ;;
  esac
done

# Check if URL is provided
if [ -z "$URL" ]; then
  echo "Usage: $0 -u URL [options]"
  exit 3
fi

# Prepare curl command
CURL_CMD="curl -w %{http_code};%{time_total} -o /dev/null -s $HTTP_METHOD $FOLLOW_REDIRECTS $INSECURE $HEADERS $RESOLVE $TIMEOUT $URL"

# Print curl command if requested
if [ "$PRINT_CURL" = "yes" ]; then
  echo "$CURL_CMD"
  exit 0
fi

# Execute curl command
CURL_OUTPUT=$($CURL_CMD)
CURL_EXIT=$?

# Parse curl output
HTTP_CODE=$(echo "$CURL_OUTPUT" | cut -d ';' -f 1)
RESPONSE_TIME=$(echo "$CURL_OUTPUT" | cut -d ';' -f 2 | xargs printf "%0.2f\n")

# Check curl exit status
if [ $CURL_EXIT -ne 0 ]; then
  case $CURL_EXIT in
  1)
    msg="CRITICAL - Unsupported protocol"
    ;;
  2)
    msg="CRITICAL - Failed to initialize"
    ;;
  3)
    msg="CRITICAL - Malformed URL"
    ;;
  4)
    msg="CRITICAL - Feature or option not enabled"
    ;;
  5)
    msg="CRITICAL - Couldn't resolve proxy"
    ;;
  6)
    msg="CRITICAL - Could not resolve host"
    ;;
  7)
    msg="CRITICAL - Could not connect to host"
    ;;
  8)
    msg="CRITICAL - Unknown FTP server response"
    ;;
  9)
    msg="CRITICAL - FTP access denied"
    ;;
  10)
    msg="CRITICAL - FTP accept failed"
    ;;
  11)
    msg="CRITICAL - FTP weird PASS reply"
    ;;
  12)
    msg="CRITICAL - FTP timeout during active session"
    ;;
  13)
    msg="CRITICAL - Unknown response to FTP PASV command"
    ;;
  14)
    msg="CRITICAL - Unknown FTP 227 format"
    ;;
  15)
    msg="CRITICAL - FTP cannot get host"
    ;;
  16)
    msg="CRITICAL - HTTP/2 error"
    ;;
  17)
    msg="CRITICAL - FTP could not set binary"
    ;;
  18)
    msg="CRITICAL - Partial file"
    ;;
  19)
    msg="CRITICAL - FTP could not download/access the given file"
    ;;
  # Skipping 20 as it is not used
  21)
    msg="CRITICAL - Quote error"
    ;;
  22)
    msg="CRITICAL - Server returned http code >= 400"
    ;;
  23)
    msg="CRITICAL - Write error"
    ;;
  # Skipping 24 as it is not used
  25)
    msg="CRITICAL - Upload failed"
    ;;
  26)
    msg="CRITICAL - Read error"
    ;;
  27)
    msg="CRITICAL - Out of memory"
    ;;
  28)
    msg="CRITICAL - Operation timeout"
    ;;
  # Skipping 29 and 30 as they are not used
  31)
    msg="CRITICAL - FTP could not use REST"
    ;;
  # Skipping 32 as it is not used
  33)
    msg="CRITICAL - HTTP range error"
    ;;
  34)
    msg="CRITICAL - HTTP post error"
    ;;
  35)
    msg="CRITICAL - A TLS/SSL connect error"
    ;;
  36)
    msg="CRITICAL - Bad download resume"
    ;;
  37)
    msg="CRITICAL - Couldn't read the given file when using the FILE:// scheme"
    ;;
  38)
    msg="CRITICAL - LDAP cannot bind"
    ;;
  39)
    msg="CRITICAL - LDAP search failed"
    ;;
  # Skipping 40 and 41 as they are not used
  42)
    msg="CRITICAL - Aborted by callback"
    ;;
  43)
    msg="CRITICAL - Bad function argument"
    ;;
  # Skipping 44 as it is not used
  45)
    msg="CRITICAL - Interface error"
    ;;
  # Skipping 46 as it is not used
  47)
    msg="CRITICAL - Too many redirects"
    ;;
  48)
    msg="CRITICAL - Unknown option specified to libcurl"
    ;;
  49)
    msg="CRITICAL - Malformed telnet option"
    ;;
  # Skipping 50 as it is not used
  51)
    msg="CRITICAL - The server's SSL/TLS certificate or SSH fingerprint failed verification"
    ;;
  52)
    msg="CRITICAL - Server returned empty response"
    ;;
  53)
    msg="CRITICAL - SSL crypto engine not found"
    ;;
  54)
    msg="CRITICAL - Cannot set SSL crypto engine as default"
    ;;
  55)
    msg="CRITICAL - Failed sending network data"
    ;;
  56)
    msg="CRITICAL - Failure receiving network data"
    ;;
  # Skipping 57 as it is not used
  58)
    msg="CRITICAL - Problem with the local certificate"
    ;;
  59)
    msg="CRITICAL - Couldn't use the specified SSL cipher"
    ;;
  60)
    msg="CRITICAL - SSL/TLS connection problem"
    ;;
  61)
    msg="CRITICAL - Unrecognized transfer encoding"
    ;;
  # Skipping 62 as it is not used
  63)
    msg="CRITICAL - Maximum file size exceeded"
    ;;
  64)
    msg="CRITICAL - Requested SSL (TLS) level failed"
    ;;
  65)
    msg="CRITICAL - Sending the data requires a rewind that failed"
    ;;
  66)
    msg="CRITICAL - Failed to initialize the OpenSSL SSL Engine"
    ;;
  67)
    msg="CRITICAL - The user name, password, or similar was not accepted and curl failed to log in"
    ;;
  68)
    msg="CRITICAL - File not found on TFTP server"
    ;;
  69)
    msg="CRITICAL - Permission problem on TFTP server"
    ;;
  70)
    msg="CRITICAL - Out of disk space on TFTP server"
    ;;
  71)
    msg="CRITICAL - Illegal TFTP operation"
    ;;
  72)
    msg="CRITICAL - Unknown TFTP transfer ID"
    ;;
  73)
    msg="CRITICAL - File already exists (TFTP)"
    ;;
  74)
    msg="CRITICAL - No such user (TFTP)"
    ;;
  # Skipping 75 and 76 as they are not used
  77)
    msg="CRITICAL - Problem with reading the SSL CA cert"
    ;;
  78)
    msg="CRITICAL - The resource (file) referenced in the URL does not exist"
    ;;
  79)
    msg="CRITICAL - An unspecified error occurred during the SSH session"
    ;;
  80)
    msg="CRITICAL - Failed to shut down the SSL connection"
    ;;
  # Skipping 81 as it is not used
  82)
    msg="CRITICAL - Could not load CRL file, missing or wrong format"
    ;;
  83)
    msg="CRITICAL - TLS certificate issuer check failed"
    ;;
  84)
    msg="CRITICAL - The FTP PRET command failed"
    ;;
  85)
    msg="CRITICAL - RTSP, mismatch of CSeq numbers"
    ;;
  86)
    msg="CRITICAL - RTSP, mismatch of Session Identifiers"
    ;;
  87)
    msg="CRITICAL - Unable to parse FTP file list"
    ;;
  88)
    msg="CRITICAL - FTP chunk callback reported error"
    ;;
  89)
    msg="CRITICAL - No connection available, the session will be queued"
    ;;
  90)
    msg="CRITICAL - SSL public key does not match pinned public key"
    ;;
  91)
    msg="CRITICAL - Invalid SSL certificate status"
    ;;
  92)
    msg="CRITICAL - Stream error in HTTP/2 framing layer"
    ;;
  93)
    msg="CRITICAL - An API function was called from inside a callback"
    ;;
  94)
    msg="CRITICAL - Authentication error"
    ;;
  95)
    msg="CRITICAL - HTTP/3 layer error"
    ;;
  96)
    msg="CRITICAL - QUIC connection error"
    ;;
  97)
    msg="CRITICAL - Proxy handshake error"
    ;;
  98)
    msg="CRITICAL - A TLS client certificate is required but was not provided"
    ;;
  99)
    msg="CRITICAL - An internal call to poll() or select() returned error that is not recoverable"
    ;;
  *)
    echo "UNKNOWN - $CURL_EXIT"
    exit 3
    ;;
  esac
  echo "$msg"
  exit 2
fi

RESPONSE_TIME_MS=$(echo "$RESPONSE_TIME * 1000" | bc | xargs printf "%0.0f\n")
perfdata="response_time=${RESPONSE_TIME_MS}ms;${WARN_TIME};${CRIT_TIME};0;"

# Check HTTP code
if [ -n "$EXPECTED_STATUS_CODE" ]; then
  if [ "$HTTP_CODE" != "$EXPECTED_STATUS_CODE" ]; then
    echo "CRITICAL - server returned HTTP code $HTTP_CODE, expected $EXPECTED_STATUS_CODE"
    exit 2
  fi
elif [ "$IGNORE_STATUS" != "yes" ] && [ "$HTTP_CODE" != 200 ]; then
  echo "CRITICAL - server returned HTTP code $HTTP_CODE"
  exit 2
fi

# Check response time
if [ $(echo "$RESPONSE_TIME_MS > $CRIT_TIME" | bc) -eq 1 ]; then
  echo "CRITICAL - Response time $RESPONSE_TIME seconds | $perfdata"
  exit 2
elif [ $(echo "$RESPONSE_TIME_MS > $WARN_TIME" | bc) -eq 1 ]; then
  echo "WARNING - response time $RESPONSE_TIME seconds | $perfdata"
  exit 1
fi

# Check critical string
BODY_CONTAINS=""
if [ -n "$CRIT_STRING" ]; then
  BODY=$(curl -s $FOLLOW_REDIRECTS $INSECURE "$HEADERS" $RESOLVE $TIMEOUT "$URL")
  # shellcheck disable=SC2076
  if ! [[ $BODY =~ "$CRIT_STRING" ]]; then
      if $SANITIZE_HTML; then
        BODY=$(echo "$BODY" | sed 's/</\&lt;/g' | sed 's/>/\&gt;/g')
      fi
    echo "CRITICAL - response body does not contain the required string: $BODY"
    exit 2
  else
    BODY_CONTAINS=", and contained substring"
  fi
fi

# All checks passed

if $DISABLE_PERFDATA && [ "$HTTP_CODE" != 200 ]; then
  perfdata_str=""
else
  perfdata_str="| $perfdata"
fi

echo "OK - response time was $RESPONSE_TIME seconds, code $HTTP_CODE${BODY_CONTAINS}. $perfdata_str"
exit 0